The present invention relates to a character recognition method and apparatus, and more particularly, to a character recognition method and apparatus for calculating similarity between an input pattern and standard patterns.
A typical conventional character recognition apparatus such as an OCR (Optical Character Reader) optically reads a character and converts the read data into a character pattern (input pattern). A pattern similarity calculation circuit incorporated in the apparatus calculates the similarity between the character pattern and standard patterns stored in an internal dictionary. The apparatus outputs a standard pattern having the highest similarity in the calculation results as a recognition result. Usually, the pattern similarity calculation circuit requires a plurality of nonvolatile memories in order to raise the process speed. A standard pattern data for one character is divided into a plurality of portions and stored into these memories as described in Japanese Patent Publication (Kokoku) No. 58-56911. The data from the memories are latched into the pattern similarity calculation circuit, which selectively outputs data by a predetermined number of bits.
FIG. 8 shows a configuration of a pattern similarity calculation circuit according to the conventional character recognition apparatus, in which standard pattern data for one character is discretely stored into a plurality of memories. According to FIG. 8, the standard pattern data for one character is divided into 9 segments (.phi..sub.N1 -.phi..sub.N9) and stored in the memories 81 to 83. More specifically, .phi..sub.N1, .phi..sub.N4 and .phi..sub.N7 are stored in the memory 81; .phi..sub.N2, .phi..sub.N5 and .phi..sub.N8, in the memory 82; and .phi..sub.N3, .phi..sub.N6 and .phi..sub.N9, in the memory 83.
However, the above conventional character recognition apparatus has the following drawbacks:
(1) The number of memories will increase as calculation speed becomes higher. This results in raising the cost of memory packaging. PA0 (2) If the input speed of an input pattern exceeds the calculation speed of the pattern similarity calculation circuit, the input pattern has to queue up to be calculated. For this reason, in order to control the input speed and input timing, a circuit for controlling the input speed must be added. Accordingly, the total throughput is limited by the input speed. PA0 (3) In the case where a standard pattern in a specific address area in a ROM where the dictionary is stored is used, e.g., in a dictionary ROM in which Chinese characters, alphabets and numerals are stored, numerals are required for recognition but the corresponding address area is being accessed, the process must wait for the termination of the current process accessing the address area, causing time loss. PA0 (4) If calculation is performed using a different similarity calculation algorithm, the current algorithm for driving the calculation circuit must be changed. This prolongs the processing time.